Bug 1726863 - Cache/elide GLContext::BindFramebuffer calls. r=lsalzman

Differential Revision: https://phabricator.services.mozilla.com/D123275

dom/canvas/WebGLContext.cpp

@@ -635,6 +635,7 @@ void WebGLContext::FinishInit() {
   // Initial setup.
 
   gl->mImplicitMakeCurrent = true;
+  gl->mElideDuplicateBindFramebuffers = true;
 
   const auto& size = mDefaultFB->mSize;
 

gfx/gl/GLContext.cpp

@@ -2158,39 +2158,72 @@ void GLContext::fCopyTexImage2D(GLenum target, GLint level,
   AfterGLReadCall();
 }
 
-void GLContext::fGetIntegerv(GLenum pname, GLint* params) const {
+void GLContext::fGetIntegerv(const GLenum pname, GLint* const params) const {
+  const auto AssertBinding = [&](const char* const name, const GLenum binding,
+                                 const GLuint expected) {
+    if (MOZ_LIKELY(!mDebugFlags)) return;
+    GLuint actual = 0;
+    raw_fGetIntegerv(binding, (GLint*)&actual);
+    if (actual != expected) {
+      gfxCriticalError() << "Misprediction: " << name << " expected "
+                         << expected << ", was " << actual;
+    }
+  };
+
   switch (pname) {
     case LOCAL_GL_MAX_TEXTURE_SIZE:
       MOZ_ASSERT(mMaxTextureSize > 0);
       *params = mMaxTextureSize;
-      break;
+      return;
 
     case LOCAL_GL_MAX_CUBE_MAP_TEXTURE_SIZE:
       MOZ_ASSERT(mMaxCubeMapTextureSize > 0);
       *params = mMaxCubeMapTextureSize;
-      break;
+      return;
 
     case LOCAL_GL_MAX_RENDERBUFFER_SIZE:
       MOZ_ASSERT(mMaxRenderbufferSize > 0);
       *params = mMaxRenderbufferSize;
-      break;
+      return;
 
     case LOCAL_GL_VIEWPORT:
       for (size_t i = 0; i < 4; i++) {
         params[i] = mViewportRect[i];
       }
-      break;
+      return;
 
     case LOCAL_GL_SCISSOR_BOX:
       for (size_t i = 0; i < 4; i++) {
         params[i] = mScissorRect[i];
       }
+      return;
+
+    case LOCAL_GL_DRAW_FRAMEBUFFER_BINDING:
+      if (mElideDuplicateBindFramebuffers) {
+        static_assert(LOCAL_GL_DRAW_FRAMEBUFFER_BINDING ==
+                      LOCAL_GL_FRAMEBUFFER_BINDING);
+        AssertBinding("GL_DRAW_FRAMEBUFFER_BINDING",
+                      LOCAL_GL_DRAW_FRAMEBUFFER_BINDING, mCachedDrawFb);
+        *params = static_cast<GLint>(mCachedDrawFb);
+        return;
+      }
+      break;
+
+    case LOCAL_GL_READ_FRAMEBUFFER_BINDING:
+      if (mElideDuplicateBindFramebuffers) {
+        if (IsSupported(GLFeature::framebuffer_blit)) {
+          AssertBinding("GL_READ_FRAMEBUFFER_BINDING",
+                        LOCAL_GL_READ_FRAMEBUFFER_BINDING, mCachedReadFb);
+        }
+        *params = static_cast<GLint>(mCachedReadFb);
+        return;
+      }
       break;
 
     default:
-      raw_fGetIntegerv(pname, params);
       break;
   }
+  raw_fGetIntegerv(pname, params);
 }
 
 void GLContext::fReadPixels(GLint x, GLint y, GLsizei width, GLsizei height,

gfx/gl/GLContext.h

@@ -27,6 +27,7 @@
 #  define MOZ_GL_DEBUG 1
 #endif
 
+#include "mozilla/IntegerRange.h"
 #include "mozilla/RefPtr.h"
 #include "mozilla/UniquePtr.h"
 #include "mozilla/ThreadLocal.h"
@@ -2019,10 +2020,49 @@ class GLContext : public GenericAtomicRefCounted, public SupportsWeakPtr {
     AFTER_GL_CALL;
   }
 
-  void fBindFramebuffer(GLenum target, GLuint framebuffer) {
+ private:
+  mutable GLuint mCachedDrawFb = 0;
+  mutable GLuint mCachedReadFb = 0;
+
+ public:
+  bool mElideDuplicateBindFramebuffers = false;
+
+  void fBindFramebuffer(const GLenum target, const GLuint fb) const {
+    if (mElideDuplicateBindFramebuffers) {
+      MOZ_ASSERT(mCachedDrawFb ==
+                 GetIntAs<GLuint>(LOCAL_GL_DRAW_FRAMEBUFFER_BINDING));
+      MOZ_ASSERT(mCachedReadFb ==
+                 GetIntAs<GLuint>(LOCAL_GL_READ_FRAMEBUFFER_BINDING));
+
+      switch (target) {
+        case LOCAL_GL_FRAMEBUFFER:
+          if (mCachedDrawFb == fb && mCachedReadFb == fb) return;
+          break;
+        case LOCAL_GL_DRAW_FRAMEBUFFER:
+          if (mCachedDrawFb == fb) return;
+          break;
+        case LOCAL_GL_READ_FRAMEBUFFER:
+          if (mCachedReadFb == fb) return;
+          break;
+      }
+    }
+
     BEFORE_GL_CALL;
-    mSymbols.fBindFramebuffer(target, framebuffer);
+    mSymbols.fBindFramebuffer(target, fb);
     AFTER_GL_CALL;
+
+    switch (target) {
+      case LOCAL_GL_FRAMEBUFFER:
+        mCachedDrawFb = fb;
+        mCachedReadFb = fb;
+        break;
+      case LOCAL_GL_DRAW_FRAMEBUFFER:
+        mCachedDrawFb = fb;
+        break;
+      case LOCAL_GL_READ_FRAMEBUFFER:
+        mCachedReadFb = fb;
+        break;
+    }
   }
 
   void fBindRenderbuffer(GLenum target, GLuint renderbuffer) {
@@ -2286,6 +2326,16 @@ class GLContext : public GenericAtomicRefCounted, public SupportsWeakPtr {
     BEFORE_GL_CALL;
     mSymbols.fDeleteFramebuffers(n, names);
     AFTER_GL_CALL;
+
+    for (const auto i : IntegerRange(n)) {
+      const auto fb = names[i];
+      if (mCachedDrawFb == fb) {
+        mCachedDrawFb = 0;
+      }
+      if (mCachedReadFb == fb) {
+        mCachedReadFb = 0;
+      }
+    }
   }
 
   void raw_fDeleteRenderbuffers(GLsizei n, const GLuint* names) {